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    <a class="edit-page-link" href="https://github.com/facebook/react/tree/master/docs/docs/addons-create-fragment.md" target="_blank">Edit on GitHub</a>
    <h1>
      Keyed Fragments
    </h1>
    <div class="subHeader"></div>

    <p><strong>Importing</strong></p>
<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="kr">import</span> <span class="nx">createFragment</span> <span class="nx">from</span> <span class="s1">&#39;react-addons-create-fragment&#39;</span><span class="p">;</span> <span class="c1">// ES6</span>
<span class="kd">var</span> <span class="nx">createFragment</span> <span class="o">=</span> <span class="nx">require</span><span class="p">(</span><span class="s1">&#39;react-addons-create-fragment&#39;</span><span class="p">);</span> <span class="c1">// ES5 with npm</span>
</code></pre></div>
<h2>Overview</h2>

<p>In most cases, you can use the <code>key</code> prop to specify keys on the elements you&#39;re returning from <code>render</code>. However, this breaks down in one situation: if you have two sets of children that you need to reorder, there&#39;s no way to put a key on each set without adding a wrapper element.</p>

<p>That is, if you have a component such as:</p>
<div class="highlight"><pre><code class="language-js" data-lang="js"><span class="kd">function</span> <span class="nx">Swapper</span><span class="p">(</span><span class="nx">props</span><span class="p">)</span> <span class="p">{</span>
  <span class="kd">let</span> <span class="nx">children</span><span class="p">;</span>
  <span class="k">if</span> <span class="p">(</span><span class="nx">props</span><span class="p">.</span><span class="nx">swapped</span><span class="p">)</span> <span class="p">{</span>
    <span class="nx">children</span> <span class="o">=</span> <span class="p">[</span><span class="nx">props</span><span class="p">.</span><span class="nx">rightChildren</span><span class="p">,</span> <span class="nx">props</span><span class="p">.</span><span class="nx">leftChildren</span><span class="p">];</span>
  <span class="p">}</span> <span class="k">else</span> <span class="p">{</span>
    <span class="nx">children</span> <span class="o">=</span> <span class="p">[</span><span class="nx">props</span><span class="p">.</span><span class="nx">leftChildren</span><span class="p">,</span> <span class="nx">props</span><span class="p">.</span><span class="nx">rightChildren</span><span class="p">];</span>
  <span class="p">}</span>
  <span class="k">return</span> <span class="o">&lt;</span><span class="nx">div</span><span class="o">&gt;</span><span class="p">{</span><span class="nx">children</span><span class="p">}</span><span class="o">&lt;</span><span class="err">/div&gt;;</span>
<span class="p">}</span>
</code></pre></div>
<p>The children will unmount and remount as you change the <code>swapped</code> prop because there aren&#39;t any keys marked on the two sets of children.</p>

<p>To solve this problem, you can use the <code>createFragment</code> add-on to give keys to the sets of children.</p>

<h4><code>Array&lt;ReactNode&gt; createFragment(object children)</code></h4>

<p>Instead of creating arrays, we write:</p>
<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="kr">import</span> <span class="nx">createFragment</span> <span class="nx">from</span> <span class="s1">&#39;react-addons-create-fragment&#39;</span><span class="p">;</span>

<span class="kd">function</span> <span class="nx">Swapper</span><span class="p">(</span><span class="nx">props</span><span class="p">)</span> <span class="p">{</span>
  <span class="kd">let</span> <span class="nx">children</span><span class="p">;</span>
  <span class="k">if</span> <span class="p">(</span><span class="nx">props</span><span class="p">.</span><span class="nx">swapped</span><span class="p">)</span> <span class="p">{</span>
    <span class="nx">children</span> <span class="o">=</span> <span class="nx">createFragment</span><span class="p">({</span>
      <span class="nx">right</span><span class="o">:</span> <span class="nx">props</span><span class="p">.</span><span class="nx">rightChildren</span><span class="p">,</span>
      <span class="nx">left</span><span class="o">:</span> <span class="nx">props</span><span class="p">.</span><span class="nx">leftChildren</span>
    <span class="p">});</span>
  <span class="p">}</span> <span class="k">else</span> <span class="p">{</span>
    <span class="nx">children</span> <span class="o">=</span> <span class="nx">createFragment</span><span class="p">({</span>
      <span class="nx">left</span><span class="o">:</span> <span class="nx">props</span><span class="p">.</span><span class="nx">leftChildren</span><span class="p">,</span>
      <span class="nx">right</span><span class="o">:</span> <span class="nx">props</span><span class="p">.</span><span class="nx">rightChildren</span>
    <span class="p">});</span>
  <span class="p">}</span>
  <span class="k">return</span> <span class="o">&lt;</span><span class="nx">div</span><span class="o">&gt;</span><span class="p">{</span><span class="nx">children</span><span class="p">}</span><span class="o">&lt;</span><span class="err">/div&gt;;</span>
<span class="p">}</span>
</code></pre></div>
<p>The keys of the passed object (that is, <code>left</code> and <code>right</code>) are used as keys for the entire set of children, and the order of the object&#39;s keys is used to determine the order of the rendered children. With this change, the two sets of children will be properly reordered in the DOM without unmounting.</p>

<p>The return value of <code>createFragment</code> should be treated as an opaque object; you can use the <a href="https://facebook.github.io/react/docs/react-api.html#react.children"><code>React.Children</code></a> helpers to loop through a fragment but should not access it directly. Note also that we&#39;re relying on the JavaScript engine preserving object enumeration order here, which is not guaranteed by the spec but is implemented by all major browsers and VMs for objects with non-numeric keys.</p>


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